The present invention relates, in general, to a method of treating intervertebral discs to relieve back pain and, more particularly, a method of treating an intervertebral disc by using a light energy diffuser placed within the annulus of an intervertebral disc, while avoiding the nucleus of the intervertebral disc, and using the diffuser to heat a damaged portion of an annulus of the intervertebral disc by diffusing light energy directly into the annulus of the intervertebral disc.
Degenerative disc disorders are difficult to treat. The normal pathway for treatment of lower back pain starts with a number of minimally invasive treatments including medications and exercise. Spinal surgery, such as spinal fusion or ablation of the nucleus, can also be used, but such surgeries are generally avoided because they are very invasive. A less invasive procedure is percutaneously applying heat to the annulus of the intervertebral disc.
Damage to the intervertebral disc in the spine is the main cause of lower back pain. The intervertebral disc, sometimes called a spinal disc or a disc, is a capsule with an annulus, comprising collagen, surrounding an inner volume called the nucleus. The nucleus contains a gel-like material. Damage to the annulus triggers the body to attempt to repair the injury. The repair attempt results in blood vessels and nerves growing into the damaged area of the annulus. It is believed that these new nerve endings are the source of xe2x80x9cdiscogenic painxe2x80x9d and low back pain. Damage to the annulus also can result in weakening and bulging of the intervertebral disc. If the bulging puts pressure on nerve roots from the spinal cord the result is pain and nerve dysfunction.
It is well known that collagen responds to heat by shrinking and stiffening. In a damaged intervertebral disc where the damage has resulted in a bulge, heating the annulus to shrink the collagen in the annulus can help reduce the bulge. Heating the annulus to stiffen the collagen is also beneficial because the stiffer annulus reduces excessive movement of the spine. In addition, the heat applied to the annulus to shrink the collagen is beneficial because it damages or destroys nerve endings that may have grown into the damaged annulus thereby reducing the ability of the nerves to transmit pain. The combination of shrinking the collagen in the annulus and damaging or destroying the unwanted nerve endings is thought to be beneficial in reducing back pain.
Physicians have treated intervertebral disc pain utilizing radiofrequency current and lasers to damage nerve endings that have grown into the annulus. U.S. Pat. No. 5,433,739 to Sluijter et al describes a method of treating disc pain by utilizing radiofrequency current to heat the nucleus of an intervertebral disc. The nucleus is heated to a higher temperature than the annulus to transfer heat to the annulus of the intervertebral disc to raise the temperature of the intervertebral disc to a level that damages unwanted ingrown nerve endings. In U.S. Pat. No. 5,571,147, Sluijter et al describe a method of using laser light for heating the nucleus of an intervertebral disc.
Physicians have also treated disc pain utilizing lasers to ablate or vaporize the nucleus of an intervertebral disc. U.S. Pat. No. 5,958,008 to Daikuzono describes using a laser to vaporize the nucleus of an intervertebral disc.
Physicians have also treated disc pain by utilizing an electrically heated wire placed through the nucleus of an intervertebral disc to heat the annulus of the intervertebral disc to a temperature sufficient to cause the collagen in the annulus to shrink. The wire, which is heated by resistive heating, transfers heat by conduction to surrounding tissues. U.S. Pat. No. 6,122,549 to Sharkey et al describes a method to treat disc pain utilizing thermal resistive electric heating.
Ablating the nucleus or heating the annulus by inserting devices through the nucleus necessitates disturbing the tissues of the nucleus. It would be less invasive to avoid inserting devices into the nucleus by directly entering a damaged portion of the annulus from the outside of the annulus. Devices that heat by diffuse light energy use radiation to cause faster heat transfer and lower heating times than conduction. The faster heat transfer can be used to controllably heat a damaged zone of the annulus while maintaining adjacent tissues, such as the nucleus, at a temperature below that which would cause degradation. It would, therefore, be advantageous to develop a method of controllably heating an annulus of an intervertebral disc by diffusing light energy directly into the annulus, avoiding the nucleus, to avoid disturbing tissues such as the nucleus. It would further be advantageous to develop a method of controllably diffusing light energy directly into the intervertebral disc utilizing optical temperature feedback and control. It would further be advantageous to controllably and directly heat a portion of the annulus of an intervertebral disc utilizing light energy to avoid damaging a healthy portion of the spine.
The present invention is directed to a method of heating the annulus of an intervertebral disc by inserting a light diffuser directly into the annulus of an intervertebral disc from outside the disc while avoiding the nucleus. The present invention further includes a method of controllably shrinking collagen in the annulus of a intervertebral disc using a diffuse light source placed within the annulus to emit diffuse light energy directly into the annulus, optically measuring the temperature of the heated tissue, and adjusting light intensity based on the measured temperature. In particular, in a method according to the present invention, an optical fiber including a diffuser is placed into the annulus of an intervertebral disc percutaneously through a small diameter piercing needle or trocar. The fiber""s diffuser is introduced from outside the annulus while avoiding the nucleus of the intervertebral disc. The fiber""s diffuser is advanced to an area within the annulus needing heat to shrink collagen or to damage nerve endings. The light generator, such as a laser, is programmed to deliver light energy to raise the temperature of a region of the annulus tissue to a predetermined temperature for a predetermined length of time. The temperature can be, for example, a temperature sufficient to produce nerve damage of ingrown unwanted nerve endings in the annulus of an intervertebral disc or a temperature sufficient to produce shrinkage of collagen in the annulus of an intervertebral disc. In an optical fiber and light generator useful for an embodiment of the present invention, temperature monitoring of tissue near the optical fiber can be accomplished using fluorescent material placed within the optical fiber. The fluorescent material, when illuminated with a light in a wavelength emitted by the light generator, fluoresces with a light that decays in intensity with a time delay dependent upon the temperature of tissue near the material. Computerized control within the light generator monitors the returned fluorescent signal and controls power output and light intensity to control temperature of tissue near the optical fiber. A method according to the present invention further includes heating the annulus using an advantageous optical fiber that includes a continuous, unitary outer sleeve.
Detailed illustrative embodiments of laser fibers for implementing the present invention are disclosed. However, it should be recognized that various alternate structural elements may occur to those skilled in the art, some of which may be different from those specific structural and functional details that are disclosed.